Disk-based storage devices such as hard disk drives (HDDs) are used to provide non-volatile data storage in a wide variety of different types of data processing systems. A typical HDD comprises a spindle which holds one or more flat circular storage disks, also referred to as platters. Each storage disk comprises a substrate made from a non-magnetic material, such as aluminum or glass, which is coated with one or more thin layers of magnetic material. In operation, data is read from and written to tracks of the storage disk via a read/write head that is moved precisely across the disk surface by a positioning arm as the disk spins at high speed.
HDDs often include a system-on-chip (SOC) to process data from a computer or other processing device into a suitable form to be written to the storage disk, and to transform signal waveforms read back from the storage disk into data for delivery to the computer. The SOC has extensive digital circuitry and has typically utilized advanced complementary metal-oxide-semiconductor (CMOS) technologies to meet cost and performance objectives. The HDD also generally includes a preamplifier that interfaces the SOC to the read/write head used to read data from and write data to the storage disk.
The preamplifier typically comprises write drivers that include bipolar transistors and associated MOS degeneration circuitry. Each of the write drivers may also have an associated data path that includes one or more high-speed CMOS inverter chains. The data paths generally need to pass very narrow pulse widths in order to provide the desired overshoot current for a given write pulse. For example, a data path may be required to provide a 130 picosecond pulse width over process, voltage and temperature (PVT) variations, where the 130 picosecond pulse width is utilized for write pulse overshoot. However, it can be difficult to support these narrow pulse width requirements using conventional voltage regulators that have fixed reference voltage circuits.
Attempts to address this issue in conventional practice include increasing the size of the inverters of the CMOS inverter chains, but such an approach unduly increases the circuit area and power consumption of the preamplifier.